氨甲酰化低密度脂蛋白诱导内皮细胞死亡：与肾病患者动脉粥样硬化的关联。

Carbamylated low-density lipoprotein induces death of endothelial cells: a link to atherosclerosis in patients with kidney disease.

作者信息

Ok Ercan, Basnakian Alexei G, Apostolov Eugene O, Barri Yousri M, Shah Sudhir V

机构信息

University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.

出版信息

Kidney Int. 2005 Jul;68(1):173-8. doi: 10.1111/j.1523-1755.2005.00391.x.

DOI:10.1111/j.1523-1755.2005.00391.x

PMID:15954906

Abstract

BACKGROUND

The presence of accelerated atherosclerosis in patients with kidney disease cannot be entirely explained by traditional cardiovascular risk factors. Exposure to urea, which is normally present in human blood plasma and elevated in patients with kidney disease, leads to the carbamylation of proteins. We postulated that low-density lipoprotein (LDL) carbamylated by urea has biologic effects relevant to atherosclerosis.

METHODS

To produce carbamylated LDL (cLDL), human native LDL (nLDL) was chemically modified in vitro by exposure to potassium cyanate. Human coronary artery endothelial cells (HCAECs) and human coronary artery smooth muscle cells (CASMCs) were treated in vitro with cLDL or nLDL. Irreversible cell death was measured using the lactate dehydrogenase (LDH) assay, apoptosis was assessed by annexin V binding, and proliferation was determined using bromodeoxyuridine (BrdU) incorporation. Total plasma protein carbamylation and plasma cLDL were measured in hemodialysis patients using the homocitrulline assay and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Our studies demonstrated that cLDL but not nLDL induced dose-dependent vascular cell injuries relevant to atherosclerosis, which included the proliferation of vascular smooth muscle cells and endothelial cell death. Under light microscopy, endothelial cells treated with cLDL showed signs of morphologic alterations. The injury to endothelial cells measured by LDH release was time-dependent and correlated with the degree of LDL carbamylation. At least a part of the endothelial cell population treated with cLDL died by apoptosis. In patients with advanced renal disease on hemodialysis, total plasma protein carbamylation and plasma cLDL were several times higher than in control healthy individuals.

CONCLUSION

Collectively these data suggest the potential role of carbamylated LDL in accelerated atherosclerosis in patients with chronic renal disease and, possibly, in healthy individuals.

摘要

背景

肾病患者中加速动脉粥样硬化的存在不能完全由传统心血管危险因素来解释。接触通常存在于人体血浆中且在肾病患者中升高的尿素会导致蛋白质氨甲酰化。我们推测，经尿素氨甲酰化的低密度脂蛋白（LDL）具有与动脉粥样硬化相关的生物学效应。

方法

为制备氨甲酰化LDL（cLDL），将人天然LDL（nLDL）在体外通过暴露于氰酸钾进行化学修饰。将人冠状动脉内皮细胞（HCAECs）和人冠状动脉平滑肌细胞（CASMCs）在体外用cLDL或nLDL处理。使用乳酸脱氢酶（LDH）测定法测量不可逆细胞死亡，通过膜联蛋白V结合评估细胞凋亡，并使用溴脱氧尿苷（BrdU）掺入法测定细胞增殖。使用高同型瓜氨酸测定法和酶联免疫吸附测定（ELISA）测量血液透析患者的总血浆蛋白氨甲酰化和血浆cLDL。

结果

我们的研究表明，cLDL而非nLDL会诱导与动脉粥样硬化相关的剂量依赖性血管细胞损伤，其中包括血管平滑肌细胞增殖和内皮细胞死亡。在光学显微镜下，用cLDL处理的内皮细胞显示出形态学改变的迹象。通过LDH释放测量的内皮细胞损伤是时间依赖性的，并且与LDL氨甲酰化程度相关。至少一部分用cLDL处理的内皮细胞群体通过凋亡死亡。在接受血液透析的晚期肾病患者中，总血浆蛋白氨甲酰化和血浆cLDL比健康对照个体高几倍。